Adaptive equalizer tap stepsize

Abstract

An apparatus comprises an adaptive filter having groups of taps, each group comprising at least one tap having an associated tap value; and a controller for selecting a scaling factor for at least one group of taps as a function of tap values of the group. The controller further adjusts an error value as a function of the selected scaling factor. The adaptive filter adapts tap values of the at least one group of taps as a function of the adjusted error value.

1 . A receiver comprising:
 an adaptive filter having groups of taps, each group comprising at least one tap having an associated tap value; and   a controller for selecting a scaling factor for at least one group of taps as a function of tap values of the group and for adjusting an error value as a function of the selected scaling factor;   wherein the adaptive filter adapts tap values of the at least one group of taps as a function of the adjusted error value.   
   
   
       2 . The receiver of  claim 1 , wherein the adaptive filter is a part of an equalizer. 
   
   
       3 . The receiver of  claim 1 , wherein the controller multiples the error value by the selected scaling factor to provide the adjusted error value. 
   
   
       4 . The receiver of  claim 1 , wherein the controller determines a maximum tap value for the at least one group of taps and selects the scale factor as a function of the determined maximum tap value. 
   
   
       5 . The receiver of  claim 4 , wherein the controller selects the scale factor by comparing the determined maximum tap value to a plurality of thresholds, each threshold associated with a particular scale factor. 
   
   
       6 . A receiver comprising:
 an equalizer having groups of taps, each group comprising at least one tap having an associated tap value; and   wherein the equalizer adjusts tap values in each group, wherein the tap values of at least one group are adjusted as a function of a stepsize, the value of which is selected as a function of tap values of the group.   
   
   
       7 . The receiver of  claim 6 , further comprising:
 a selector for provided the selected stepsize, wherein the selector determines a maximum tap value for the at least one group and selects the stepsize as a function of the determined maximum tap value.   
   
   
       8 . The receiver of  claim 7 , wherein the selector is a part of the equalizer. 
   
   
       9 . The receiver of  claim 7 , wherein the selector multiples an error value by the selected stepsize to provide an adjusted error value, which is used by the equalizer for adjusting the tap values of the at least one group. 
   
   
       10 . The receiver of  claim 7 , wherein the selector selects the stepsize by comparing the determined maximum tap value to a plurality of thresholds, each threshold associated with a particular stepsize. 
   
   
       11 . A method for use in a receiver, the method comprising:
 adaptively filtering a signal with an adaptive filter having a number of taps, wherein the number of taps comprises a plurality of tap groups, each tap group having at least one tap;   determining an error value as a function of the filtered signal;   adjusting the error value as a function of tap values of at least one of the tap groups to provide an adjusted error value; and   adapting the taps of the at least one of the tap groups as a function of the adjusted error value.   
   
   
       12 . The method of  claim 11 , wherein the adjusting step includes:
 selecting a scaling factor as a function of the tap values of the at least one of the tap groups; and   multiplying the error value by the selected scaling factor to provide the adjusted error value.   
   
   
       13 . The method of  claim 12 , wherein the selecting step includes:
 determining a maximum tap value for the tap group; and   selecting the scale factor as a function of the determined maximum tap value.   
   
   
       14 . The method of  claim 13 , wherein the selecting the scale factor step includes:
 comparing the determined maximum tap value to a plurality of thresholds, each threshold associated with a particular scale factor   
   
   
       15 . A method for use in a receiver, the method comprising:
 equalizing a signal with an equalizer to provide an equalized signal, the equalizer having a plurality of tap groups, each tap group having at least one tap;   determining an error value as a function of the equalized signal;   adjusting the error value to provide an adjusted error value; and   adapting tap values of at least one of the plurality of tap groups as a function of the adjusted error value.   
   
   
       16 . The method of  claim 15 , wherein the adjusting step includes:
 selecting a stepsize as a function of tap values of the at least one tap group; and   adjusting the error value as a function of the selected stepsize to provide the adjusted error signal.   
   
   
       17 . The method of  claim 16 , wherein the adjusting the error value step includes:
 multiplying the error value by the selected stepsize to provide the adjusted error signal.   
   
   
       18 . The method of  claim 16 , wherein the selecting step includes:
 determining a maximum tap value from the taps values of the at least one tap group; and   selecting the stepsize as a function of the determined maximum tap value.   
   
   
       19 . The method of  claim 18 , wherein the selecting the stepsize step include:
 comparing the determined maximum tap value to a plurality of thresholds, each threshold associated with a particular stepsize.